1. Field of Invention
Example embodiments of the present invention relate to semiconductor manufacturing equipment and methods thereof. In particular, example embodiments of the present invention relate to an electrostatic chuck (ESC) with a temperature sensing unit, exposure equipment having the ESC, and a method of detecting temperature from the surface of a photomask.
2. Description of Related Art
A photolithography process, which may be one of the processes performed during semiconductor fabrication, generally includes the operations of coating a photoresist on a wafer, exposing the photoresist of a wafer illuminated by light that is projected or reflected on a desired and/or predetermined photomask (reticle) and the wafer coated with the photoresist, and developing to form a circuit pattern by imprinting the photoresist on the wafer exposed by the light.
At least in part due to the desire for high integration semiconductor devices, increasingly small and precise photolithography processes are being used and/or required to form photoresist patterns. A permissible width of the photoresist may be determined by Rayleigh's Equation.R=k1*λ/NA  (Rayleigh's Equation)In the above equation, R is resolution, k1 is a process constant, λ is a wavelength of light source, and NA is a diameter of lens. The resolution R in Rayleigh's Equation may be decreased by decreasing the process constant k1, shortening the wavelength λ, and/or enlarging the lens diameter NA. Shortening the wavelength of light to less than the wavelength of light produced by a Krypton Flouride (KrF) laser having a 248 nm wavelength or shortening the wavelength of light to less than the wavelength of light produced by an Argon Flouride (ArF) laser having 193 nm wavelength may involve conducting an exposure process using an extreme ultraviolet (EUV) light source. The EUV light source may have a wavelength of 13.4 nm, for example.
However, a conventional exposure process using EUV are different from exposure processes using a KrF light source having a wavelength of 248 nm or ArF light source having a wavelength of 193 nm. For example, a conventional exposure process using a KrF light source or ArF light source may proceed at atmosphere and may employ a photomask that transmits light. Edges of the transparent or semi-transparent photomask may be fixed to a chuck by an absorption force in a conventional device.
However, because EUV has a very short wavelength that may be about 13.4 nm, EUV light is generally absorbed or becomes extinct while passing through most media, for example, air or quartz. In order to prevent the absorption or extinction of EUV light, an exposure process with EUV light may be conducted almost in a vacuum and may use a reflective photomask.
In conventional exposure processes using EUV light, the photomask may locally heat up because of the irradiation of light, which may result in the deformation of patterns formed on the photomask. For example, the size and shape of the patterns may vary due to thermal expansion. Further, because quartz, which is generally used as a substrate, has a small thermal conductivity, temperature is irregularly distributed over the substrate. Thus, circuit patterns may vary based on variations in temperature, which may cause difficulty in completing desired patterns.